The present invention relates to a photopolymerizable mixture that can be developed with aqueous solutions, containing a polymeric binder, a polymerizable compound having at least one ethylenically-unsaturated double bond in the molecule, and a photoinitiator or photoinitiator system. This mixture is suitable for the production of photosensitive recording materials, in particular of planographic printing plates and photoresists.
Photopolymerizable mixtures containing water-soluble binders are described in DE 15 22 362 and DE 19 17 917. As a rule, these mixtures can be developed readily and without scumming, but they suffer from the disadvantage that in planographic printing the hardened image areas, which contain the water-soluble binder, are wetted more easily by the dampening solutions and are attacked by the latter during the production of high print runs.
Mixtures of the above generic type are also described in DE 20 53 363. The binders described therein comprise reaction products obtained from a polymer containing hydroxyl groups or amino groups and at least one saturated alkyl sulfonyl isocyanate, alkoxy sulfonyl isocyanate, aryl sulfonyl isocyanate or aryloxy sulfonyl isocyanate. In combination with diazonium salt condensation products or photopolymerizable mixtures, the binder is processed to give photosensitive layers. However, the resulting mixtures can only be developed with aqueous-alkaline solutions if the binders employed have high acid numbers, which adversely affect the abrasion resistance and printing properties of the hardened layers.
EP 167 963 describes a negative-working photosensitive mixture suitable for the production of planographic printing plates comprising a diazonium salt polycondensation product, an ethylenically-unsaturated compound which can be polymerized by a free-radical process, a photo-initiator and a water-insoluble polymeric binder. High print runs can be achieved when polyvinyl acetals are used as binders. In this case development can, however, only be performed with solutions comprising predominantly organic solvents.
In DE 37 32 089 graft polymers are described, which comprise a polyurethane as the graft backbone and grafted-on vinyl ester units, which are at least partially saponified to give vinyl alcohol units. The polymers are suitable as binders for pigments; for preparing printing inks, thermoplastic adhesives and solvent-containing adhesives; as constituents of varnishes or coatings for fibers, films and metals, and for thermoplastic shaped articles.
JP 246,047/87 describes photopolymerizable mixtures wherein graft polymers of polyurethanes and polyvinyl alcohol with mercapto groups are contained as binders.
Graft polymers obtained from the graft polymers described in DE 37 32 089 above, by acetalizing with aldehydes, are described in German Patent Application P 38 35 840.9.
German Patent Application P 38 24 146.3 discloses photocurable elastomeric mixtures containing a compound polymerizable by a free-radical process, a photo-initiator and, as the binder, a graft polymer according to DE 37 32 089, which is soluble or dispersible in an aqueous solution.